Many factors contribute to development and maintenance of renal hypertension. Carotid sinus baroreceptor function is one factor, and much remains to be learned about its role in pathogenesis of renovascular hypertension. Specific goals of the present study are: First, to determine quantitatively whether during chronic phase of "one-kidney" and "two-kidney" Goldblatt renal hypertension carotid sinus baroreceptors undergo adaptive changes ("resetting"). Second, if "resetting" occurs, then to determine whether adaptive changes involve mechanical properties of the carotid sinus wall elements or the receptor neural elements. And third, to determine whether sympathetic efferents to the carotid sinus region modulate "resetting" in one or both types of hypertension models. Experimental design consists of producing one-kidney and two-kidney Goldblatt renal hypertension in dogs in which sympathetic efferents to one carotid sinus have been cut. Once hypertension is established, pressure-nerve and pressure-deformation relationships from "sympathetic-intact" and "sympathetic-denervated" carotid sinuses of each hypertensive model will be compared with each other and with their respective sham-operated controls. Statistical and quantitative analyses of results will be used to define the extent, locus, and modulating role of sympathetic efferents in baroreceptor adaptation in renal hypertension. The results should enhance our understanding of the role of baroreceptor function in pathogenesis of human renovascular hypertension, and should provide further quantitative data for rigorous diagnosis and clinical management of this disease.